Background

Pott disease, also known as tuberculous spondylitis, is one of the oldest demonstrated diseases of humankind, having been documented in spinal remains from the Iron Age in Europe and in ancient mummies from Egypt and the Pacific coast of South America.[1, 2] In 1779, Percivall Pott, for whom the disease is named, presented the classic description of spinal tuberculosis. (See the image below.)[3]

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MRI of a 31-year-old man with tuberculosis of the spine. Images show the thoracic spine before and after an infusion of intravenous gadolinium contras....

Since the advent of antituberculous drugs and improved public health measures, spinal tuberculosis has become rare in industrialized countries, although it is still a significant cause of disease in developing nations. Tuberculous involvement of the spine has the potential to cause serious morbidity, including permanent neurologic deficits and severe deformities. Medical treatment or combined medical and surgical strategies can control the disease in most patients.

Patient education

Patients with Pott disease should be instructed on the importance of therapy compliance. For patient education information, see the Infections Center, as well as Tuberculosis.

Pathophysiology

Pott disease is usually secondary to an extraspinal source of infection. Pott disease manifests as a combination of osteomyelitis and arthritis that usually involves more than 1 vertebra. The anterior aspect of the vertebral body adjacent to the subchondral plate is usually affected. Tuberculosis may spread from that area to adjacent intervertebral disks. In adults, disk disease is secondary to the spread of infection from the vertebral body. In children, the disk, because it is vascularized, can be the primary site.[4]

Progressive bone destruction leads to vertebral collapse and kyphosis. The spinal canal can be narrowed by abscesses, granulation tissue, or direct dural invasion, leading to spinal cord compression and neurologic deficits.

The kyphotic deformity is caused by collapse in the anterior spine. Lesions in the thoracic spine are more likely to lead to kyphosis than those in the lumbar spine. A cold abscess can occur if the infection extends to adjacent ligaments and soft tissues. Abscesses in the lumbar region may descend down the sheath of the psoas to the femoral trigone region and eventually erode into the skin.

Epidemiology

Occurrence in the United States

Although the incidence of tuberculosis increased in the late 1980s to early 1990s, the total number of cases has decreased in recent years. The frequency of extrapulmonary tuberculosis has remained stable.

Bone and soft-tissue tuberculosis accounts for approximately 10-15% of extrapulmonary tuberculosis cases and between 1% and 2% of total cases. Tuberculous spondylitis is the most common manifestation of musculoskeletal tuberculosis, accounting for approximately 40-50% of cases. These figures are roughly similar for North American and international series.[5, 6]

International occurrence

Approximately 1-2% of total tuberculosis cases are attributable to Pott disease. In the Netherlands, between 1993 and 2001, tuberculosis of the bone and joints accounted for 3.5% of all tuberculosis cases (0.2-1.1% in patients of European origin, and 2.3-6.3% in patients of non-European origin).[7]

Race-, sex-, and age-related demographics

Data from Los Angeles and New York show that musculoskeletal tuberculosis affects primarily African Americans, Hispanic Americans, Asian Americans, and foreign-born individuals.

As with other forms of tuberculosis, the frequency of Pott Disease is related to socioeconomic factors and historical exposure to the infection.

Although some series have found that Pott disease does not have a sexual predilection, the disease is more common in males (male-to-female ratio of 1.5-2:1).

In the United States and other developed countries, Pott disease occurs primarily in adults. In countries with higher rates of Pott disease, involvement in young adults and older children predominates.[8, 9]

Prognosis

Current treatment modalities are highly effective against Pott disease if the disorder is not complicated by severe deformity or established neurologic deficit.

Deformity and motor deficit are the most serious consequences of Pott disease and continue to be a serious problem when diagnosis is delayed or presentation of the patient is in advanced stages of the disease.[10]

Paraplegia resulting from cord compression caused by the active disease usually responds well to chemotherapy. However, paraplegia can manifest or persist during healing because of permanent spinal cord damage.

Operative decompression can greatly increase the recovery rate, offering a means of treatment when medical therapy does not bring rapid improvement.

Careful long-term follow up is also recommended, since late-onset complications can still occur (disease reactivation, late instability or deformity).[11]

Morbidity

Pott disease is the most dangerous form of musculoskeletal tuberculosis because it can cause bone destruction, deformity, and paraplegia.

Pott disease most commonly involves the thoracic and lumbosacral spine. However, published series have shown some variation.[12, 13, 14, 15] The lower thoracic vertebrae make up the most common area of involvement (40-50%), followed closely by the lumbar spine (35-45%). In other series, proportions are similar but favor lumbar spine involvement.[16] Approximately 10% of Pott disease cases involve the cervical spine.

History

The presentation of Pott disease depends on the following[17] :

Stage of disease

Affected site

Presence of complications such as neurologic deficits, abscesses, or sinus tracts

Potential constitutional symptoms of Pott disease include fever and weight loss. The reported average duration of symptoms at diagnosis is 4 months[13] but can be considerably longer.[15, 18] This is due to the nonspecific presentation of chronic back pain.

Back pain is the earliest and most common symptom of Pott disease, with patients usually experiencing this problem for weeks before seeking treatment. The pain caused by Pott disease can be spinal or radicular.

Cervical spine tuberculosis is a less common presentation but is potentially more serious because severe neurologic complications are more likely. This condition is characterized by pain and stiffness. Patients with lower cervical spine disease can present with dysphagia or stridor. Symptoms can also include torticollis, hoarseness, and neurologic deficits.

The clinical presentation of spinal tuberculosis in patients infected with the human immunodeficiency virus (HIV) is similar to that of patients who are HIV negative; however, spinal tuberculosis seems to be more common in persons infected with HIV.[19]

Physical Examination

The physical examination in Pott disease should include the following:

Careful assessment of spinal alignment

Inspection of skin, with attention to detection of sinuses

Abdominal evaluation for subcutaneous flank mass

Meticulous neurologic examination

Although the thoracic and lumbar spinal segments are nearly equally affected in persons with Pott disease, the thoracic spine is frequently reported as the most common site of involvement. Together, these segments make up 80-90% of spinal tuberculosis sites, with the remaining cases of Pott disease occurring in the cervical spine. Almost all patients with Pott disease have some degree of spine deformity (kyphosis).

Examination should reveal local pain related to the affected area or radicular pain. Muscle spasm and rigidity can also be associated.

Large, cold abscesses of paraspinal tissues or psoas muscle may protrude under the inguinal ligament and may erode into the perineum or gluteal area.

Neurologic deficits may occur early in the course of Pott disease. Signs of such deficits depend on the level of spinal cord or nerve root compression.

Pott disease that involves the upper cervical spine can cause rapidly progressive symptoms. Retropharyngeal abscesses occur in almost all cases affecting this part of the spine. Neurologic manifestations occur early and range from a single nerve palsy to hemiparesis or quadriplegia.

A large proportion of patients with Pott disease do not present with extraskeletal disease. In reported series, only 10-38% of cases of Pott disease are associated with extraskeletal tuberculosis.

With regard to the above-mentioned microbiologic studies, bone tissue or abscess samples are obtained to stain for acid-fast bacilli (AFB), and organisms are isolated for culture and susceptibility. Procedures guided by computed tomography (CT) scanning can be used to guide percutaneous sampling of affected bone or soft-tissue structures. These study findings are positive in only about 50% of the cases.

Biopsy

Percutaneous, CT scan ̶ guided needle biopsy of bone lesions is a safe procedure that also allows therapeutic drainage of large paraspinal abscesses. Obtain a tissue sample for microbiologic and pathologic studies to confirm diagnosis and to isolate organisms for culture and susceptibility. Positive culture yield of percutaneous is 50-83% and appears to be influenced by technical details, such as decontamination of specimens prior to culture.[20]

Histologic findings

Because microbiologic studies may be nondiagnostic of Pott disease, anatomic pathology can be significant. Gross pathologic findings include exudative granulation tissue with interspersed abscesses. Coalescence of abscesses results in areas of caseating necrosis.

Drainage

Some cases of Pott disease are diagnosed following an open drainage procedure (eg, following presentation with acute neurologic deterioration).

Scintigraphy

Radionuclide scanning findings are not specific for Pott disease. Gallium and technetium bone scans yield high false-negative rates (70% and up to 35%, respectively).[21]

CT scanning reveals early lesions and is more effective for defining the shape and calcification of soft-tissue abscesses. In contrast to pyogenic disease, calcification is common in tuberculous lesions.

MRI

Magnetic resonance imaging (MRI) is the criterion standard for evaluating disk-space infection and osteomyelitis of the spine and is most effective for demonstrating the extension of disease into soft tissues and the spread of tuberculous debris under the anterior and posterior longitudinal ligaments.[6] MRI is also the most effective imaging study for demonstrating neural compression.[24, 25]

Contrast-enhanced MRI findings are useful in differentiating tuberculous spondylitis from pyogenic spondylitis. MRI findings in Pott disease include thin and smooth enhancement of the abscess wall and a well-defined paraspinal abnormal signal. Thick and irregular enhancement of the abscess wall and an ill-defined paraspinal abnormal signal suggest pyogenic spondylitis.[26] The images below are studies of a man aged 31 years with spinal tuberculosis.

View Image

MRI of a 31-year-old man with tuberculosis of the spine. Images show the thoracic spine before and after an infusion of intravenous gadolinium contras....

View Image

MRI of the T11 in a 31-year-old man with tuberculosis of the spine. Extensive bone destruction consistent with tuberculous osteomyelitis is evident. T....

Approach Considerations

Before the advent of effective antituberculosis chemotherapy, Pott disease was treated with immobilization using prolonged bed rest or a body cast. At the time, the disease carried a mortality rate of 20%, and relapse was common (30%).

The duration of treatment, surgical indications, and inpatient care for Pott disease have since evolved. Opinions differ regarding whether the treatment of choice should be conservative chemotherapy or a combination of chemotherapy and surgery. The treatment decision should be individualized for each patient, although routine surgery does not seem to be indicated.[27]

Devices

Despite questionable efficacy, prolonged recumbence and the use of frames, plaster beds, plaster jackets, and braces are still used.

Cast or brace immobilization was a traditional form of treatment but has generally been discarded. Patients with Pott disease should be treated with external bracing.

Inpatient care

Once the diagnosis of Pott disease is established and treatment is started, the duration of hospitalization depends on the need for surgery and the clinical stability of the patient.

Follow-up

Patients with Pott disease should be closely monitored to assess their response to therapy and compliance with medication. Directly observed therapy may be required.

The development or progression of neurologic deficits, spinal deformity, or intractable pain should be considered evidence of poor therapeutic response. This raises the possibility of antimicrobial drug resistance, as well as the necessity for surgery.

Because of the risk of deformity exacerbations, children with Pott disease should undergo long-term follow-up until their entire growth potential is completed.[28] Older patients can also present with late-onset complications such as reactivation, instability, or deformity. Observation is warranted in all groups of patients.

Consultations

Pharmacologic Therapy

According to recommendations issued in 2003 by the US Centers for Disease Control and Prevention (CDC), the Infectious Diseases Society of America, and the American Thoracic Society, a 4-drug regimen should be used empirically to treat Pott disease.[1]

Isoniazid and rifampin should be administered during the whole course of therapy. Additional drugs are administered during the first 2 months of therapy. These are generally chosen from among the first-line drugs, which include pyrazinamide, ethambutol, and streptomycin. The use of second-line drugs is indicated in cases of drug resistance.[29]

Treatment duration

Studies performed by the British Medical Research Council indicate that tuberculous spondylitis of the thoracolumbar spine should be treated with combination chemotherapy for 6-9 months.[5]

However, the research council’s studies did not include patients with multiple vertebral involvement, cervical lesions, or major neurologic involvement. Because of these limitations, many experts still recommend chemotherapy for 9-12 months.

For selected cases with surgical indication that allows complete debridement of the lesion, a combination of surgery and ultra-shortened course of therapy (4.5 mo), appears to show comparable outcomes of a combination of surgery and 9 months of drug therapy.[30]

Surgical Indications and Contraindications

Indications

While most patients should respond to medical treatment, a surgical approach needs to be evaluated and considered. Indications for surgical treatment of Pott disease generally include the following[31, 32] :

No response to medical therapy - Continuing progression of kyphosis or instability

Large paraspinal abscess

Nondiagnostic percutaneous needle biopsy sample

Resources and experience are key factors in the decision to use a surgical approach. The lesion site, extent of vertebral destruction, and presence of cord compression or spinal deformity determine the specific operative approach (kyphosis, paraplegia, tuberculous abscess).[33]

Vertebral damage is considered significant if more than 50% of the vertebral body is collapsed or destroyed or a spinal deformity of more than 5° exists.

The most conventional approaches include anterior radical focal debridement and posterior stabilization with instrumentation. The specific advantages and limitations of surgical techniques are unclear. Individualization of the case is of greatest importance.[16, 34, 35, 36, 37] Newer modalities and techniques are being reported, such as thoracoscopic decompression.[38]

In Pott disease that involves the cervical spine, the following factors justify early surgical intervention:

High frequency and severity of neurologic deficits

Severe abscess compression that may induce dysphagia or asphyxia

Instability of the cervical spine

Contraindications

Vertebral collapse of a lesser magnitude is not considered an indication for surgery because, with appropriate treatment and therapy compliance, it is less likely to progress to a severe deformity.

Medication Summary

A 4-drug regimen should be used empirically to treat Pott disease. Treatment can be adjusted when susceptibility information becomes available.

Isoniazid and rifampin should be administered during the whole course of therapy. Additional drugs are administered during the first 2 months of therapy and are generally chosen from among the first-line drugs, such as pyrazinamide, ethambutol, and streptomycin. (A 3-drug regimen usually includes isoniazid, rifampin, and pyrazinamide.) In cases of drug resistance, the use of second-line medications is indicated.

The duration of treatment is somewhat controversial. Although some studies favor a 6- to 9-month course, traditional courses range from 9 months to longer than 1 year. The duration of therapy should be individualized and based on the resolution of active symptoms and the clinical stability of the patient.

Pyrazinamide

Clinical Context:
Pyrazinamide is bactericidal against M tuberculosis in an acid environment (macrophages). It has good absorption from the GI tract and penetrates well into most tissues, including the cerebrospinal fluid (CSF).

Streptomycin

Clinical Context:
Streptomycin is bactericidal in an alkaline environment. Because it is not absorbed from the GI tract, the drug must be administered parenterally. Streptomycin exerts action mainly on extracellular tubercle bacilli. Only about 10% of the drug penetrates cells that harbor organisms. Streptomycin enters the CSF only in the presence of meningeal inflammation. Excretion is almost entirely renal.

MRI of a 31-year-old man with tuberculosis of the spine. Images show the thoracic spine before and after an infusion of intravenous gadolinium contrast. The abscess and subsequent destruction of the T11-T12 disc interspace is marked with arrowheads. Vertebral body alignment is normal. Courtesy of Mark C. Diamond, MD, and J. Antonio Bouffard, MD, Detroit, Mich.

MRI of a 31-year-old man with tuberculosis of the spine. Images show the thoracic spine before and after an infusion of intravenous gadolinium contrast. The abscess and subsequent destruction of the T11-T12 disc interspace is marked with arrowheads. Vertebral body alignment is normal. Courtesy of Mark C. Diamond, MD, and J. Antonio Bouffard, MD, Detroit, Mich.

MRI of the T11 in a 31-year-old man with tuberculosis of the spine. Extensive bone destruction consistent with tuberculous osteomyelitis is evident. The spinal cord has normal caliber and signal. No evidence of spinal cord compression or significant spinal stenosis is distinguishable. Courtesy of Mark C. Diamond, MD, and J. Antonio Bouffard, MD, Detroit, Mich.

MRI of a 31-year-old man with tuberculosis of the spine. Images show the thoracic spine before and after an infusion of intravenous gadolinium contrast. The abscess and subsequent destruction of the T11-T12 disc interspace is marked with arrowheads. Vertebral body alignment is normal. Courtesy of Mark C. Diamond, MD, and J. Antonio Bouffard, MD, Detroit, Mich.

MRI of the T11 in a 31-year-old man with tuberculosis of the spine. Extensive bone destruction consistent with tuberculous osteomyelitis is evident. The spinal cord has normal caliber and signal. No evidence of spinal cord compression or significant spinal stenosis is distinguishable. Courtesy of Mark C. Diamond, MD, and J. Antonio Bouffard, MD, Detroit, Mich.